A. Field of the Invention
The safety system of this invention is usable to control flow of fluids in a well wherein the well environment may include high pressure conditions, such as 20,000 psi gas pressures; high corrosive fluids, such as H.sub.2 S or CO.sub.2 ; and/or high temperatures, all of which are detrimental to resilient seals.
B. The Prior Art
The combination of a tubing safety valve and an annulus safety valve to control flow of fluids within a well is disclosed by U.S. Pat. No. 3,035,642 to J. S. Page; U.S. Pat. No. 3,313,350 to J. S. Page, Jr.; and U.S. Pat. No. 3,252,476 to J. S. Page, Jr. Annulus safety valves for controlling flow in the annulus between concentric well pipe are disclosed by U.S. Pat. Nos. 3,045,755; 3,156,300; both to Page, et al and U.S. Pat. No. 3,299,955 to J. S. Page, Jr.
Some of the aforementioned safety valves have been commercialized as illustrated on pages 4115 through 4117 of the "COMPOSITE CATALOGUE OF OIL FIELD EQUIPMENT & SERVICES", 1974-1975 edition.
The present annulus safety valves in combination with tubing safety valves, provide controlled flow through concentric well pipes. However, in the high temperature, high corrosive, and/or high pressure environment of some wells, these annulus safety valves are insufficient.
The valve member of the aforementioned U.S. Pat. Nos. 3,035,642; 3,253,476; and 3,156,300; and the valve member illustrated in the "COMPOSITE CATALOGUE" is moved in response to pressurizing a pressure chamber. The resilient seals of the pressure chamber are exposed to the well environment even after the valve member closes the annulus flow path. The high corrosive, and/or high temperature well environment could deteriorate these resilient seals and high pressure well fluids could blowout through the pressure chamber.
All of the aforementioned annulus safety valves utilize a sleeve valve member with resilient seals to block the annulus flow. The resilient seals may deteriorate and leak. It is not economically feasible to obtain a metal to metal seal with a sleeve valve member because expansions and contractions due to temperature variations cannot be accommodated and because sand collects around the sleeve valve member and inhibits a good metal to metal seal. Also, with a sleeve valve, the higher the fluid pressure of the fluid contained by the valve, the greater the tendency of the valve to leak.
The aforementioned annulus valves, except for the U.S. Pat. No. 3,035,642, disclose utilizing a valve member which closes the annulus flow path at a position other than at its upstream end. Additionally the valve housing is not integral. Therefore, potential leak paths from the annulus flow path through the valve housing exist. Even though the valve member closes the annulus flow path, the safety valve could fail to perform its function of shutting in the well due to a leakage through one of these potential leak paths.
The aforementioned annulus valves, except for the U.S. Pat. No. 3,035,642, all have a tortuous annulus flow path. High velocity flow of well fluids through these tortuous flow paths cause flow cutting of valve components and/or the surrounding well pipe.
The aforementioned U.S. Pat. No. 3,035,642 has a metal to resilient seal between a sleeve valve member and a resilient packer. The resilient seat could deteriorate in a high corrosive well environment preventing a good seal with the sleeve valve member.
Problems with the aforementioned annulus safety valves can be summarized as follows: Valve components, including the operating means for the valve member, are subject to downhole well fluids even though the valve member is in a position closing the annulus flow path. There is more than one seal location, and thus additional structures to seal, even though the valve member is in a flow path closing position. The greater the well pressure the greater the likelihood that the valve will fail due to leakage past the sleeve valve member. The resilient seals may deteriorate and/or prove ineffective in some well environments. Additionally the tortuous flow path through the valve member results in flow cutting of either the valve member or the surrounding well pipe.